%I A081238
%S A081238 0,2,4,4,6,12,16,16,16,24,30,30,36,48,60,60,70,70,80,80,96,112,126,126,
%T A081238 126,144,144,144,160,176,192,192,216,240,264,264,286,312,338,338,364,
%U A081238 390,416,416,416,448,476,476,476,476,510,510,540,540,576,576,612,648
%N A081238 #{(i,j): mu(i)*mu(j) = -1, 1<=i<=n, 1<=j<=n}, where mu=A008683 (Moebius 
               function).
%C A081238 a(n) + A081239(n) + A081240(n) = n^2;
%C A081238 a(n) = a(n-1) iff mu(n) = 0.
%e A081238 n mu(n) ... n: 1 2 3 4 5 6 7 8
%e A081238 - ------ .... |---------------->
%e A081238 1 .. +1 ..... | + - - 0 - + - 0
%e A081238 2 .. -1 ..... | - + + 0 + - + 0
%e A081238 3 .. -1 ..... | - + + 0 + - + 0
%e A081238 4 ... 0 ..... | 0 0 0 0 0 0 0 0
%e A081238 5 .. -1 ..... | - + + 0 + - + 0 a(8)=16, as there are
%e A081238 6 .. +1 ..... | + - - 0 - + - 0 16 '-1's in the 8x8-square
%e A081238 7 .. -1 ..... | - + + 0 + - + 0 (represented as '-')
%e A081238 8 ... 0 ..... | 0 0 0 0 0 0 0 0.
%Y A081238 Cf. A070549.
%Y A081238 Sequence in context: A112921 A008133 A022471 this_sequence A002086 A039830 
               A159788
%Y A081238 Adjacent sequences: A081235 A081236 A081237 this_sequence A081239 A081240 
               A081241
%K A081238 nonn
%O A081238 1,2
%A A081238 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 11 2003